In magnetic resonance, a spin echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. The spin echo spectrometer possesses an extremely high energy resolution (roughly one part in 100,000). Additionally, it measures the density-density correlation (or intermediate scattering function) F(Q,t) as a function of momentum transfer Q and time. Other neutron scattering techniques measure the dynamic structure factor S(Q,ω), which can be converted to F(Q,t) by a Fourier transform, which may be difficult in practice. For weak inelastic features S(Q,ω) is better suited, however, for (slow) relaxations the natural representation
is given by F(Q,t). Because of its extraordinary high effective energy resolution compared to other neutron scattering techniques, NSE is an ideal method to observe[2]overdamped internal dynamic modes (relaxations) and other diffusive processes in materials such as a polymer blends, alkane chains, or microemulsions.
^Callaway, D. J.; Farago, B; Bu, Z (2013). "Nanoscale protein dynamics: A new frontier for neutron spin echo spectroscopy". The European Physical Journal E. 36 (7): 76. doi:10.1140/epje/i2013-13076-1. PMID23884624. S2CID10246098.
^Higgins JS, Benoit HC (1997). Polymers and neutron scattering. Oxford Series on Neutron Scattering in Condensed Matter (Book 8). Clarendon Press. ISBN978-0198500636.